Leaf springs are used in suspensions for small utility vehicles having a gross vehicle weight of between about 500 pounds and about 3000 pounds, such as Gator™ utility vehicles available from Deere and Company of Moline, Ill., to dampen vibration, increase passenger comfort, and improve vehicle handling. A pair of leaf springs may support a vehicle frame over an axle. Each leaf spring has a linear load deflection curve, or spring rate.
Cargo carrying capacity may be an important feature for small utility vehicles. Cargo combined with optional attachments added to a utility vehicle, for example, can more than double the vehicle's weight. To accommodate the additional weight and yet maintain sufficient suspension travel while loaded, some utility vehicles may be “stiffly” sprung, i.e., have leaf springs with a very high spring rate. However, a high spring rate may increase the vibration and road irregularities transferred to the operator and passengers of the vehicle.
Leaf springs having a non-linear or stepped load deflection curve, i.e., two or more spring rates, have not been widely adopted in small utility vehicles. This is due, at least in part, to the complexity and cost of dual or variable rate leaf springs, especially for use in relatively inexpensive small utility vehicles. For example, dual or variable rate leaf springs may include multiple components which may involve significantly greater assembly time.
There is a need for a simple, inexpensive dual rate leaf spring suspension for a small utility vehicle. Additionally, there is a need for a dual rate leaf spring suspension that may replace conventional leaf spring suspensions without requiring replacement of other components of a small utility vehicle.